1. Field of the Invention
This invention relates generally to an inverter including an inverter circuit developing a variable-voltage, variable-frequency source, and more particularly, to such an inverter provided with a filter circuit for reducing electrical noise and a cooling arrangement for cooling components including the filter circuit.
2. Description of the Prior Art
A switching operation of an inverter circuit accompanies electrical noise in the inverters of the above-described type. The noise sometimes causes malfunction of equipment disposed around the inverter, such as acoustic equipment. In view of this problem, a filter circuit is conventionally provided at the power supply side of the inverter to eliminate the electrical noise. FIG. 18 illustrates an example of such conventional inverter. As shown, the inverter 1 comprises a single casing 4 accommodating therein a rectifier circuit 2, an inverter circuit 3, etc. A discrete, exterior type filter circuit 5 is connected between a power supply and the inverter 1.
The inverter 1 including the discrete filter circuit 5 necessitates a large installation space when the filter circuit 5 is provided independent of the inverter 1. Furthermore, a wire connecting the filter circuit 5 to the rectifier circuit 2 and the inverter circuit 3 has an increased length and is exposed in the exterior of the casing 4. As a result, radiation noise is emitted from the wire 6. In recent years, the filter 5 has been used with the inverter in a larger number of cases so that environment around the inverter can be prevented from being adversely affected. For the above-described reasons, the filter circuit 5 is desired to be accommodated in the casing 4 together with the rectifier circuit 2, the inverter circuit 3, etc. so that the inverter is compacted.
However, when the conventional filter circuit 5 is accommodated in the casing of the inverter, the casing would become considerably larger than the conventional casing 4. Moreover, the filter circuit 5 or particularly, coils thereof generate a large amount of heat. Accordingly, an amount of heat generated in the casing is increased when the filter circuit 5 is accommodated in the casing together with the inverter circuit 3 etc. Consequently, an arrangement for sufficiently cooling the filter circuit 5 accommodated in the casing 4 is required in addition to the conventional cooling arrangement for the rectifier circuit 2, the inverter circuit 3, etc.